Hitherto, there are disclosed industrial articulated robots comprising a turning bed turning in a horizontal direction on a fixed base, a lower arm provided so that it can be inclined in forward and backward directions on the turning bed, an upper arm provided at the front end portion of the lower arm so that it can be inclined in upper and lower directions, a drive link provided so that it can be inclined in upper and lower directions on the turning bed, and a connecting link in parallel to the lower arm, which connects the upper arm and the drive link, whereby parallel link mechanism is constituted by the upper arm, the lower arm, the drive link and the connecting link, the industrial articulated robot body further comprising a turning arm rotatable about the axis along the length direction of the upper arm, and a wrist portion which can be inclined in a direction vertical to the turning axis of the turning arm (e.g., Tokkaihei No. 2-31691 (Japanese Patent Application Laid Open No. 31691/1990), Tokkaihei No. 3-202288 (Japanese Patent Application Laid Open No. 202288/1991), Tokkaihei No. 3-245980 (Japanese Patent Application Laid Open No. 245980/1991)).
However, when the turning bed is turned, it is turned in such a manner to support all weights of the lower arm, the upper arm, the turning arm, and the wrist portion which are integrally loaded on the turning bed. As a result, there were the problems that the structure of turning device for driving the turning bed becomes large and it is difficult to increase turning speed.
As means for solving this problem, there is disclosed an industrial articulated robot in which, as a parallel link mechanism including lower arm, a turning section supported at the front end portion of the lower arm so that it is turned in a horizontal direction is provided in place of directly connecting the upper arm to the lower arm front end portion so that it is maintained to be horizontal even if the lower arm is inclined; and an upper arm extending in a lateral direction from the turning section, a turning arm rotatable about the axis along the length direction of the upper arm, and a wrist portion which can be inclined in a direction vertical to the turning axis of the turning arm are further provided, whereby the turning section is adapted to support only weights of the upper arm, the turning arm and the wrist portion, thus to reduce weight as load of the turning section (e.g., Tokkaihei No. 3-104574 (Japanese Patent Application Laid Open No. 104574/1991)).
However, in the case of the Tokkaihei No. 3-104574 of the prior art, the upper arm is fixed horizontally or at a fixed angle at the turning section supported at the lower arm front end portion so that it is horizontally turned. For this reason, the upper arm is rotated in upper and lower directions together with the turning section by drive link in parallel to the turning section within the parallel link mechanism through connecting link supported at turning section end portion so that it can be rotated similarly to the conventional Tokkaihei No. 2-31691, etc.
Accordingly, since the upper arm and the lower arm carry out operation as two links intersecting with each other within parallelogram of the parallel link mechanism, the upper arm and the lower arm interfere with each other. Thus, an angle (relative angle) that the upper arm and the lower arm form was restricted, resulting in the drawback that the operation region of the upper arm is narrowed.